Ken Watanabe isn’t incredibly imposing. He speaks in a contemplative hush, often relies on his female assistant to translate, laughs as frequently as he inhales, and likes to greet new friends with a hug. He is, quite simply, the least intimidating fellow in the world.

So it’s a wonder that when fans spot the slender, 6’ 1” Watanabe in Tokyo, they avoid him. ”The characters I play are very tough, strong men,” says the 44-year-old Japanese TV star, two days after braving The Last Samurai’s frigid Manhattan premiere sans overcoat. ”I’m like fire. People don’t come near me.”

Fortunately, Samurai director Edward Zwick (Glory) wasn’t one of them. Cast opposite Tom Cruise as towering warlord Katsumoto – the actor’s first American part – Watanabe added another fiery persona to his CV. But critics have been swooning as much over the way he anchors the movie with an eerily quiet, lyric intensity as they have over his samurai skills. ”If you don’t have Katsumoto,” Cruise explains, ”you don’t have a movie.” Zwick agrees. ”His willingness to be small and still and internal is an enormous gift,” says the director, who understands how Watanabe is drawing notices for trumping his 800-pound gorilla of a costar. ”I think nobody would be happier to hear that Ken steals this movie than Tom. They became very good friends.” (So much so, Cruise adds, that ”we would sing on set. We’d make up lines and verses while shooting the battle scenes. He’s fun.”)

Not bad for a native of the Japanese coastal town of Niigata who played trumpet in the high school band before switching to contemporary theater when he realized he had no musical ability. Just don’t look to Watanabe to brag. His name, he’s quick to divulge, isn’t short for Kenneth but rather is a common moniker that means modesty. It’s no surprise then that Bushido, the traditional honor code personified by Katsumoto, comes naturally to the actor. ”It’s very simple,” he says. ”Honor, honesty, modesty, all of which we can use in daily life.” (Privacy, too: The marriage question gets a curt no comment.) They’re also qualities that led Zwick to hire him: ”He brought this extraordinary sense of having thought about life and death in a very particular way.”

And thus it was that Samurai forced Watanabe to draw on his own scary past. In 1989, he was fresh off breakouts in features (as a truck driver in Tampopo) and TV (as a feudal lord in the popular Japanese drama Masamune the One-Eyed Dragon) when he was diagnosed with leukemia. Though he glosses over it, the star laments that film offers dwindled as a result of his illness, basically confining him to TV in the ’90s. ”I couldn’t finish the film I was working on,” he says of the 1991 Japanese period epic Heaven and Earth. ”And after that many people had an idea that I couldn’t do movies – that they were too demanding.”

Ask him if he’s healthy today, however, and he smacks you on the knee, guffawing ”You saw the movie!” Sure enough, to fill out Katsumoto’s billowing robes and massive armor, Watanabe bulked up, honing his horseback and swordplay prowess and leaving stunt doubles twiddling their thumbs. Aided by speech coaches, he also sharpened a virtually nonexistent command of English until he became a de facto technical adviser.